The lawn care industry provides thatcher products which slice or rake the upper layer of the turf of grass or the like to condition the turf, such as shown and described in U.S. Pat. Nos. 2,827,751 and 2,881,847 and 4,494,365. Those three patents show assemblies of shafts and turf slicing blades, with the assembly normally being mounted forwardly on a mower or like machine for moving over the ground surface in the thatching or slicing process. Further, adjacent ones of those blades of the prior art are normally offset from each other in an end or axial view of the assembly, and the blades are also drivingly related to the mounting shaft which is rotatable. Those patents show specific ways in which the blades are related or mounted on the shaft, and other specific showings are in U.S. Pat. Nos. 949,218 and 2,149,193 and 2,244,099 and 2,551,049 and 2,781,563.
All of the aforementioned patents are distinguishable from the present invention of the appratus and method in that those patents show specific and imited arrangements for mounting the blades on the shaft. That is, the present invention provides apparatus and method for mounting the blades on the shaft in an automatic manner wherein the blades present a helical pattern along the length of the shaft, though no careful or special or specific maneuvering or positioning of the blades by the assembler is required in order to achieve the desired helical pattern.
U.S. Pat. Nos. 2,197,549 and 2,604,026 and 3,330,365 also show cutter members on a rotatable shaft or the like and with the cutting members being disposed in a helical pattern therealong. However, these patents are also similarly limited in that they require careful and specific positioning of the blades in order to achieve the helical patterns or they require that the assembly be carefully manufactured to close tolerances in order to achieve the assembly and to achieve the necessary driving torque between the shaft and the blades, such as revealed in the limitations of U.S. Pat. No. 3,330,365. In that patent, the support arbor or shaft has a plurality of keys extending therealong in helical patterns, and the blades slide over the arbor in mating relationship with the keys, for presenting the helical blade pattern. That patent discloses four splines or keys on the outer circumference of the arbor, and, where those keys might be welded, there is a problem of clearance for sliding the cutters or rings thereover. In any event, there is only minimal drive relationship for transmitting torque between the keys and the blades, and, in the assembly, the assembler must fit each of the blade key-ways onto the keys.
The present invention improves upon the prior art in the manner aforementioned, and it also does this in providing an assembly which is easily accomplished with a minimum of skill, attention, and time, so that one can readily and accurately assemble the blades and spacers onto the shaft to provide the desired helical pattern in an automatic fashion. The invention also results in minimal expense, as well as labor saving and ultimate accuracy and strength of the final assembly. Still further, the degree of helix provided with these cutting blades is such that the blades are not subject to clogging from the turf encountered thereby, and also they do a minimum of damage to the turf because of the degree of offset between adjacent blades, as related to the curvature of the helix itself. This therefore results in an improved method of assembling or attaching, indexing, and driving the blades by the rotating shaft, all in an accurate and sturdy relationship. As such, the blades of this invention can be made with less detail and attention than that required of blades heretofore provided, and the present blades can be a more desirable heat-treated steel blade.